[OMPI users] problems with parallel MPI-IO...

[Alexander Beck-Ratzka]

Hi Folks,

I am using the following f90 example program for writing a file in parallel 
with MIP:

[snip]
  program parallel_io

  use mpi

  implicit none

  integer ierr, i, myrank, BUFSIZE, thefile, intsize
  parameter (BUFSIZE=100)
  integer buf(BUFSIZE)
  !  integer (kind=MPI_OFFSET_KIND) disp
  integer*8 disp

  call mpi_init(ierr)
  call mpi_comm_rank(mpi_comm_world, myrank,ierr)

  do i=0,BUFSIZE
     buf(i) = myrank*BUFSIZE + i
     print*, 'i =', i, 'myrank =', myrank, 'buf(i)=',buf(i)
  end do

  call mpi_file_open(mpi_comm_world, 'testfile', MPI_MODE_WRONLY + 
MPI_MODE_CREATE, mpi_info_null, thefile, ierr)
  call mpi_type_size(MPI_INTEGER, intsize, ierr)

  disp = myrank * BUFSIZE * intsize

  !  call mpi_file_set_view(thefile, disp, MPI_INTEGER, MPI_INTEGER, 'native', 
mpi_info_null, ierr)
  call mpi_file_write_at(thefile, disp, buf, BUFSIZE, MPI_INTEGER, 
mpi_status_ignore, ierr)

  call mpi_file_close(thefile, ierr)
  call mpi_finalize(ierr)


end program parallel_io
[snip]


And the follwoing program shall read all the data in again, and print them out

[snip]
  program parallel_read_io

  use mpi

  implicit none

  integer ierr, i, myrank, BUFSIZE, thefile, intsize
  parameter (BUFSIZE=100)
  integer buf(BUFSIZE)
  !  integer (kind=MPI_OFFSET_KIND) disp
  integer*8 disp

  call mpi_init(ierr)
  call mpi_comm_rank(mpi_comm_world, myrank,ierr)

  !  do i=0,BUFSIZE
  !     buf(i) = myrank*BUFSIZE + i
  !  end do

  call mpi_file_open(mpi_comm_world, 'testfile', MPI_MODE_RDONLY, 
mpi_info_null, 
thefile, ierr)
  call mpi_type_size(MPI_INTEGER, intsize, ierr)

  disp = myrank * BUFSIZE * intsize

  !  call mpi_file_set_view(thefile, disp, MPI_INTEGER, MPI_INTEGER, 'native', 
mpi_info_null, ierr)
  !  call mpi_file_read(thefile, buf, BUFSIZE, MPI_INTEGER, mpi_status_ignore, 
ierr)
  call mpi_file_read_at(thefile, disp, buf, BUFSIZE, MPI_INTEGER, 
mpi_status_ignore, ierr)

  call mpi_file_close(thefile, ierr)

  !  print the data read in...

  if (myrank.eq.1) then
     do i = 0,BUFSIZE
        print*, 'i =', i, 'myrank =', myrank, 'buf(i)=', buf(i)
     end do
  endif

  call mpi_finalize(ierr)
[snip]

I have maid several tests, also with do loops only from 0 to (BUFSIZE-1), with 
MPI_FILE_SET_VIEW and MPI_FILE_READ, etc...

When I am reading the data in again and print them out, I always have:

buf(0)=0

for every rank, so I assume that something with the offset is wrong. I am using 
openmpi with an Intel f90 compiler.

What am I doing wrong?

Best wishes

Alexander